When a fine hole is formed in a workpiece by electric discharge machining, a rod-like or pipe-like electrode is used to apply a voltage between the electrode and the workpiece so that the workpiece is machined by electric discharge generated between them. As the electrode is liable to be easily exhausted when used for machining the fine hole, the used rod-like or pipe-like electrode is generally long. The thin and long electrode is liable to vibrate or flex during the electric discharge machining, which might reduce the machining accuracy. An electric discharge machine in which an electrode guiding device for supporting and guiding the electrode is employed to prevent the vibration or flexion from occurring is disclosed in Japanese Patent No. 2,952,339. In the technology described in this Japanese Patent No. 2,952,339, a fine hole machining electrode is used, and an electrode guiding device for supporting and guiding the fine hole machining electrode and an electrode-induction device for inserting the electrode into the electrode guiding device are provided. The electrode is inserted into a guide hole of the electrode guiding device while being nipped by the electrode-induction device, and a fine hole is formed by electric discharge machining while guiding the electrode by the electrode guiding device. Further, a method and an apparatus are disclosed in the U.S. Pat. No. 6,396,022, in which an electrode magazine including an electrode guide having a pipe electrode inserted therein is replaced in a spindle.
The prior art described in the above-mentioned Japanese Patent No. 2,952,339 is problematic in that the electrode-induction device is required for inserting the electrode mounted on the spindle into the electrode guiding device and in that a process for inserting the electrode into an inner hole of the electrode guide is troublesome and time-consuming because the thin and long electrode is liable to vibrate and/or flex. Also, the prior disclosed in the U.S. Pat. No. 6,396,022 is a system in which a plurality of large electrode magazines, each including a pipe-like electrode, a collet chuck for holding and guiding the pipe-like electrode and means for moving a vibration preventing guide and an electrode guide, are accommodated in advance in a magazine rack so that the electrode magazine is replaceable in the spindle, which is problematic in that a structure thereof is complicated.